Integrated circuit system for controlling structural health monitoring processes

ABSTRACT

A structural health monitoring system using ASICs for signal transmission, reception, and analysis. Incorporating structural health monitoring functionality into one or more ASICs provides a durable yet small, lightweight, low cost, and portable system that can be deployed and operated in field conditions. Such systems provide significant advantages, especially in applications such as armor structures.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional patent application of U.S. patentapplication Ser. No. 12/536,429 filed on Aug. 5, 2009, the entirecontents of which is incorporated herein by reference.

BRIEF DESCRIPTION

This invention relates generally to structural health monitoring. Morespecifically, this invention relates to an integrated circuit system forcontrolling structural health monitoring processes, and applicationstherefor.

BACKGROUND

Many current structural health monitoring techniques are not well suitedfor use outside of a controlled laboratory environment. For example,traditional nondestructive inspection techniques, such as ultrasound andX-radiography, require controlled conditions and highly trainedtechnicians. Techniques such as these are thus often inconvenient and,when the cost of setting up/maintaining such laboratory conditions isincluded, expensive. Accordingly, it is desirable to develop structuralhealth monitoring devices and techniques that are suitable for useoutside the laboratory. In particular, it is desirable to developstructural health monitoring systems capable of use in field conditions,where light-weight, small, and cost-effective systems are advantageous.

SUMMARY

The invention can be implemented in a number of ways, including as astructural health monitoring system.

In one embodiment, a structural health monitoring system comprises astructure, and at least one integrated circuit. The at least oneintegrated circuit is configured to transmit interrogating signals to aplurality of actuators coupled to the structure, to receive sensorsignals from a plurality of sensors coupled to the structure, and todetermine a health of the structure according to a comparison of thereceived sensor signals to baseline signals. The interrogating signalscorrespond to stress waves propagated through the structure so as toquery the structure, the sensor signals correspond to stress wavesdetected by the plurality of sensors, the baseline signals correspond toa baseline state of the structure, and one or more integrated circuitsof the at least one integrated circuit are coupled to the structure.

In a further embodiment, a structural health monitoring system comprisesa first integrated circuit and a second integrated circuit. The firstintegrated circuit comprises a processing block receiving sensor signalsfrom sensors affixed to a structure, comparing the sensor signals tobaseline signals, generating results data from the comparing, andgenerating interrogation signals initiating transmission ofinterrogating signals for interrogating the structure. The firstintegrated circuit also comprises a waveform generation block receivingthe interrogation signals from the processing block and generatingcorresponding ones of the interrogating signals. The second integratedcircuit comprises a signal conditioning block receiving the sensorsignals, conditioning the sensor signals, and transmitting theconditioned sensor signals for receiving by the processing block of thefirst integrated circuit. The second integrated circuit also comprises amultiplexer block routing the interrogating signals to predeterminedactuators affixed to the structure.

Other aspects and advantages of the invention will become apparent fromthe following detailed description taken in conjunction with theaccompanying drawings which illustrate, by way of example, theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference should be made tothe following detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1A is a block diagram representation of an application specificintegrated circuit (ASIC) based structural health monitoring system inaccordance with an embodiment of the invention.

FIG. 1B illustrates an exemplary flexible actuator/sensor layer for usein the system of FIG. 1A.

FIG. 2 illustrates further details of the ASICs of FIG. 1A.

FIG. 3 is a block diagram representation of an ASIC based structuralhealth monitoring system in accordance with a further embodiment of theinvention.

FIG. 4 is a flowchart illustrating one sequence of steps that systems ofthe invention can perform in order to monitor structural health.

FIG. 5 is a flowchart illustrating further details of signaltransmission/structure querying in accordance with embodiments of theinvention.

FIG. 6 is a flowchart illustrating further details of signal receptionin accordance with embodiments of the invention.

FIG. 7 is a flowchart illustrating further details of signal analysisand health determination in accordance with embodiments of theinvention.

FIG. 8A is a block diagram representation of an armor structure with anoff-board ASIC based structural health monitoring system.

FIG. 8B is a block diagram representation of an armor structure withon-board data storage and off-board ASIC based structural healthmonitoring system.

FIG. 9 is a block diagram representation of an armor structure with anon-board ASIC based structural health monitoring system.

FIG. 10 illustrates further details of construction and composition ofarmor structures.

FIG. 11 illustrates further details of armor structures for use withoff-board ASIC based structural health monitoring systems.

Like reference numerals refer to corresponding parts throughout thedrawings.

DETAILED DESCRIPTION OF EMBODIMENTS

In one embodiment, the invention relates to a structural healthmonitoring system using ASICs for signal transmission, reception, andanalysis. In contrast to current structural health monitoring systemsthat use often-cumbersome hardware, incorporating structural healthmonitoring functionality into one or more ASICs provides a durable yetsmall, lightweight, low cost, and portable system that can be deployedand operated in field conditions.

Such systems provide significant advantages, especially in applicationssuch as armor structures. Armor structures, such as ceramic plates usedin body armor, multi-layer ballistic armors, and other high-strengthstructures, are difficult to analyze in the field due to the size andweight of current nondestructive evaluation equipment, and due to theadvanced materials used. An ASIC-based system is sufficiently small andlight to be employed in field conditions, yet is also durable enough towithstand such field conditions. Such ASIC-based systems are smallenough to be deployed on/affixed to the armor itself, or can be a partof a separate portable analysis system.

FIG. 1A is a block diagram representation of one such ASIC-basedstructural health monitoring system in accordance with an embodiment ofthe invention. System 10 includes a first ASIC 20 and second ASIC 30, aconnector 40 connecting the ASICs 20, 30 to sensors/actuators 50, aswell as a power supply 60 and display 70. The sensors/actuators 50 areaffixed to a structure such as a piece of armor. The remainder of thesystem 10 can be incorporated into a single unit such as a handheldunit, or any portion thereof can be affixed to the structure. Forexample, as will be described below, the connector 40 and/or ASICs 20,30 can be affixed to the structure along with the sensors/actuators 50.

The sensors/actuators 50 can be any set of sensors and/or actuatorscapable of detecting and transmitting stress waves, respectively.Typically, sensors/actuators 50 include multiple actuating and/orsensing elements placed at discrete locations on the structure, fortransmitting stress waves through a structure and detecting resultingwaveforms, respectively. As is known, sensors can both passively monitora structure for stress waves resulting from an impact (whereuponanalysis of such stress waveforms can be performed to determine dataabout any corresponding damage), and monitor the structure for stresswaves actively transmitted through the structure by the actuators(whereupon comparison of the resulting waveforms to the original signalstransmitted can indicate damage). The invention contemplates use of anysensors and any actuators, affixed to a structure in any manner and anynumber that allow for evaluation of the structure. However, one suitablesensor/actuator is lead zirconate titanate (PZT) piezoelectrictransducers (or any other suitable transducer) that each can act as botha sensor and an actuator. In known manner, each PZT transducer convertselectrical signals to stress waves in order to actively query astructure, and converts resulting detected stress waves to electricalsignals for analysis.

Furthermore, the sensors/actuators 50 can be individually affixed to astructure, or affixed to a flexible layer that can itself be affixed toa structure. For purposes of illustration, one exemplary sensor systemis shown in FIG. 1B, which shows a flexible sensing layer that can beused in accordance with embodiments of the present invention. Adiagnostic layer 100 is shown, which contains an array of sensors 50.The sensors 50 can be any sensors, including transducers capable of bothgenerating and receiving signals used in structural health monitoringsuch as stress waves, and are connected to conductive traces 104. Thetraces 104 connect (or interconnect, if necessary) sensors 50 to one ormore output leads 106 configured for connection to a processor or otherdevice capable of analyzing the data derived from the sensors 50.

The diagnostic layer 100 and its operation are further described in U.S.Pat. No. 6,370,964 to Chang et al., which is hereby incorporated byreference in its entirety and for all purposes. Construction of thediagnostic layer 100 is also explained in U.S. Pat. No. 7,413,919 toQing et al., which is also incorporated by reference in its entirety andfor all purposes. The output leads 106 are electrically connected toconnector 40, so that the sensors 50 can be placed in electricalcommunication with ASIC 30.

The ASICs 20, 30 of system 10 are capable of acting in both “active” and“passive” modes. In active mode, the ASICs 20, 30 generate stress wavesfrom certain actuators and detect those stress waves at sensors indifferent locations from the actuators. The detected stress waves areexamined to determine how they have changed due to propagation throughthe structure, which can indicate whether they have propagated through adamaged portion of the structure, and how severe that damage is. Inpassive mode, the ASICs 20, 30 monitor sensors to detect stress wavesgenerated in the structure by impact, operational conditions, or otherevents. Analysis of these detected stress waves can indicate conditionssuch as damage, fatigue, and the like.

In particular, ASIC 20 generates waveforms and analyzes detectedsignals, while ASIC 30 directs the waveforms and detected signals to thecorrect destination, as well as amplifies and conditions the detectedsignals. In this embodiment, ASIC 20 generates querying waveforms (i.e.waveforms for generating corresponding stress waves in the structure foruse in analyzing the structure to determine its health), and outputsthem to ASIC 30 along with control signals directing ASIC 30 to sendthese waveforms to specific actuators. ASIC 30 then amplifies thequerying waveforms and routes the amplified waveforms to those actuatorsvia a multiplexer bank, where they generate corresponding stress wavesin the structure that are detected at one or more sensors. The sensorsconvert these detected stress waves to electrical signals, whereuponASIC 30 conditions and amplifies the signals, and sends them to ASIC 20for analysis. ASIC 20 receives and analyzes these signals to determinethe health of the structure.

FIG. 2 illustrates further details of the ASICs of FIG. 1A. ASIC 20 caninclude a data processing block 200, memory block 202, waveformgenerator 204, analog to digital (A/D) converter 206, digital to analog(D/A) converter 208, and interfaces 210-216. The data processing block200 is a processor such as a central processing unit (CPU) that handlessignal generation for active structure querying, and signal analysis forpassive monitoring and/or analysis of active signals detected aftertransmission through the structure. The memory 202 stores informationused by data processing block 200, such as digital representations ofwaveforms used in actively querying the structure, and baseline signaldata. The memory 202 can include re-writable memory, so that waveformsand baseline data can be added or updated as desired. A/D converter 206converts analog signals received from sensors 50 to digital signals foranalysis by data processing block 200. Waveform generator 204 generatesdigital waveforms at the instruction of data processing block 200, andD/A converter 208 converts these digital signals to analog signals forsending to actuators 50.

ASIC 30 can include amplifiers 250, 252, a signal conditioning block254, a multiplexer (MUX) bank 256, and interfaces 258-264. Theamplifiers 250, 252 amplify signals received from sensors 50 and outfrom the ASIC 20 to the actuators 50, respectively. The MUX bankconnects various different actuators/sensors 50 under direction from thedata processing block 200, so that signals are transmitted only fromspecified actuators 50, or so that only specified sensors 50 aremonitored.

It is noted that, in the embodiment of FIG. 1A, power supply 60 iselectrically connected to, and supplies power for, display 70 and bothASICs 20, 30. Power supply 60 can be any power supply suitable forproviding power to electronic components. However, the invention alsoencompasses embodiments of system 10 that are structured differently.For example, some applications such as large structures, or thickstructures on which sensors are located relatively far from each other,may require higher-voltage actuation signals (signals generated by theASICs 20, 30 for transmission by actuators 50 through their structure).When the voltages of these actuation signals are sufficiently high, itmay be desirable to move amplifier block 250 out from within ASIC 30.This may be done, for example, to avoid problems such as electricalinterference with other components of ASIC 30 or overheating/burnout ofASIC 30, and to improve the consistency of ASICs being fabricated. FIG.3 illustrates one such example. In FIG. 3, structural health monitoringsystem 300 is constructed similar to system 10 of FIG. 1A. However, ASIC302, corresponding generally to ASIC 30, does not contain an amplifier250 integrated within. Rather, a separate, dedicated power amplifier 304is employed outside of ASIC 302. In this embodiment, power amplifier 304is located a sufficient distance from the ASICs of system 300 to avoidany problems due to electrical interference or heat. Power supply 306also supplies power separately to power amplifier 304.

Power supplies 60, 306 can be any power supply suitable for supplyingrequisite power to ASICs and/or amplifiers. In particular, powersupplies 60, 306 can be battery-operated power supplies that containrelatively lightweight batteries for use in portable, in-fieldapplications.

Various hardware configurations of the invention having been described,attention now turns to aspects of their operation. FIG. 4 is a flowchartillustrating one sequence of steps that systems of the invention canperform in order to monitor structural health. As above, systems 10, 300can be operated in both active and passive modes, where the ASICs 20, 30and actuators 50 generate stress waves in active mode to actively querythe structure, and ASICs 20, 30 and sensors 50 in passive mode simplymonitor the structure to detect stress waves generated by impact,structure operation, or the like.

More specifically, FIG. 4 illustrates steps taken in active mode. Here,the ASICs 20, 30 and actuators 50 generate interrogating or queryingsignals, i.e. stress waves having specified waveforms, that aretransmitted through the structure (Step 400). These diagnostic signalspropagate through the structure and are received at specified sensors 50(Step 402), which detect the stress waves and generate correspondingelectrical signals. These electrical signals are sent to the ASICs 20,30 through connector 40, where they are digitized. Processor block 200then analyzes the digitized waveforms to determine the health orintegrity of the structure (Step 404). Results are transmitted todisplay 70 for viewing by users (Step 406).

FIGS. 5-7 illustrate further details of Steps 400-404. FIG. 5 is aflowchart illustrating further details of Step 400, i.e. the generationand transmission of diagnostic signals in active mode. In summary, ASICs20, 30 generate a specified electrical waveform and send this waveformto specified actuators 50, which convert this waveform to a stress wavethat propagates through the structure. First, processing block 200retrieves the specified waveform from memory 202 (Step 500), and directsthe waveform generator 204 to generate a corresponding digitalinterrogation waveform, i.e. a time-varying digital signal shapedaccording to the data retrieved from memory 202 and intended to generatea correspondingly-shaped interrogating stress wave propagating throughthe structure (Step 502). This digital signal is sent to D/A converter208, which converts it to an analog signal (Step 504) and sends theanalog signal across interfaces 216, 262 to amplifier 252. Amplifier 252amplifies the analog signal (Step 506) and sends the amplified signal toMUX 256.

The data processing block 200 determines which actuators 50 are totransmit the interrogating waveform into the structure, and sends acommand to MUX 256 (via interfaces 214 and 260) directing it to transmitthe amplified analog signal to those specified actuators 50 (Step 508).In response, the MUX 256 connects leads 106 from those specifiedactuators 50 to the output of amplifier 252, whereupon the amplifiedanalog signal is transmitted to those selected actuators 50 (Step 510).The actuators 50 then generate specified stress waves in the structure.

Once these stress waves are generated in the structure, they propagatethrough it and are received at other sensors 50, as described above inconnection with Step 402. FIG. 6 is a flowchart illustrating furtherdetails of this Step 402. The processor 200 determines which sensors areto be used to detect the interrogating waveforms, and sends a command toMUX 256 (again, via interfaces 214 and 260) identifying those selectedsensors 50 (Step 600). The MUX 256 responds by connecting leads 106 fromthose specified sensors 50 to signal conditioning block 254, effectivelyallowing processor 200 to monitor these sensors 50 for any stress wavesthey detect (Step 602).

Once these selected sensors 50 detect stress waves, whether the resultof interrogating signals or any other event, the sensors 50 transmitcorresponding analog electrical signals to signal conditioning block254, which conditions the signals (Step 604). Signal conditioning caninclude any operations performed on signals input to block 254 to makethose signals more readily analyzed by processor 200. These operationscan include filtering to remove/attenuate undesired frequencies and/ornoise (thus improving signal-to-noise ratio), or other operations. Theconditioned sensor signals are then sent to amplifier block 250, wherethey are amplified for more ready analysis by processor 200 (Step 606).The amplified analog signals are sent to A/D converter 206 of ASIC 20via interfaces 258 and 212, where they are converted to digital signals(Step 608) and sent to processor 200.

As above, the processor 200 commences with Step 404 once it receivesthese signals. FIG. 7 is a flowchart illustrating further details ofsignal analysis and health determination taken by processor 200 inconnection with Step 404. More specifically, the processor 200 receivesthese digital signal representations (Step 700), and retrieves baselinesignal data from memory 200 (Step 702). This baseline signal data isknown, and typically is the stored representation of the waveformreceived from the same sensor 50 that transmitted the signal received atStep 700, using the same interrogating waveform and sent from the sameactuator 50 at some previous “baseline” structure state. The baselinesignal data thus typically describes the “baseline” state of thestructure along that particular actuator/sensor path. Any changes to thestructure along this path are thus typically reflected in the signalreceived by the processor 200 at Step 700. Accordingly, the signalreceived at Step 700 is compared to this retrieved baseline signal (Step704), whereupon such a comparison can indicate changes from the baselinesignal to the currently-received signal, thus indicating a change in thestructure from its baseline state to its current state.

The comparison of Step 704 can be carried out in any manner. As oneexample, features such as the signal magnitude envelope, phasedifference between the received signal and baseline signal, peakamplitudes, total signal energy within a certain time window, frequencyspectra, or the like can be extracted by processor 200 (Step 750), andused to determine signal changes, a relevant damage index, or any otherdesired quantity (Step 752). These quantities can then be compared topreset thresholds (Step 754), which can indicate damage or anotherrelevant change in the structure if these thresholds are exceeded.

While FIGS. 5-7 illustrate further details of the steps taken inconnection with FIG. 4, one of ordinary skill in the art will observethat the invention is not limited to the steps of FIGS. 5-7. Rather, theinvention encompasses operation of ASICs 20, 30 in any manner consistentwith determination of the health of the structure being monitored. Forexample, while FIG. 4 illustrates steps taken in active mode, theinvention encompasses use of systems 10, 300 in passive mode as well. Itis thus possible to utilize systems 10, 300 to monitor structureswithout actively transmitting interrogating signals through it. In thismanner, systems 10, 300 can employ the steps of FIG. 6, without those ofFIG. 5, to monitor specified sensors 50 for any stress waves detected inthe structure. In strictly passive monitoring, no relevant baselinesignal would typically exist. Accordingly, embodiments of systems 10,300 employing such passive monitoring can then determine structurehealth by comparing the received signals from the sensors 50 againstcertain predetermined criteria. For instance, quantities such as peakamplitude and dominant signal frequencies can indicate the occurrence animpact and its severity, while the times at which peak signal amplitudesare received at various sensors 50 can be used to triangulate thelocation of the impact.

It should be noted that the invention encompasses use of systems 10, 300on any type of structure to which sensors/actuators 50 can be affixed.As above, this allows the systems of the invention to provide alightweight and portable, yet durable, structural health monitoringsystem that can be used in many different environments, and that issuitable for many different applications. One such application is themonitoring and/or analysis of armor structures such as ballisticprotective body armor. Advanced materials and configurations for suchbody armor often render other nondestructive evaluation techniquesineffective in detecting damage in modem body armor. Additionally, it isoften desirable to quickly scan body armor in field conditions, to makea rapid decision as to whether to replace a combatant's body armor.Systems of the invention that employ ASICs such as ASICs 20, 30 are thussuperior to many other nondestructive evaluation systems, in that theycan be utilized to detect damage in modem body armor, yet also aredurable and lightweight, allowing for use in field conditions. Systemsof various embodiments of the invention are thus well suited for use inconjunction with body armor, especially in field conditions.

It is also noted that systems of the invention can be utilized with bodyarmor in different ways. For example, various components of systems 10,300 can be placed on the body armor itself (“on-board”), or locatedremote therefrom (“off-board”). Additionally, the sensors/actuators 50used in conjunction with systems 10, 300 can be affixed to the surfaceof body armor or embedded within, and can be placed on a flexiblesubstrate or be separately attached to the armor.

FIG. 8A is a block diagram representation of an armor structure with anoff-board ASIC based structural health monitoring system. Here, a pieceof body armor 800 has a number of sensors/actuators 50 affixed theretoand spatially distributed thereon. As in FIG. 1B, the sensors/actuators50 have electrical leads (not shown) extending to interface 802, whichcan be any electrical interface. Signal paths 804 exist between eachpair of sensors/actuators 50, some of which are shown. As signals cantravel along each path from actuator to sensor, each signal pathrepresents a path along which the health of the structure 800 can bemonitored. The interface 802 is electrically connected to a monitoringsystem of the invention, such as system 10 or system 300. That is, theinterface 802 can be electrically connected to connector 40, so thatsignals can be sent to/from the actuators/sensors 50.

The monitoring system 10, 300 can be operated as described above, withmonitoring system 10, 300 sending electrical waveforms through interface802 to specified ones of the actuators 50 so as to generate stress wavesalong desired signal paths 804. These stress waves are detected bysensors 50 at the ends of these specified paths 804, where the sensors50 generate corresponding electrical waveforms and send them back tosystem 10, 300. Changes from a stored baseline waveform to the waveformreceived by system 10, 300 can indicate changes in the state of thestructure 800 along those paths 804.

The invention also includes embodiments in which any one or morecomponents of systems 10, 300 can be located on-board the armor, i.e.,affixed to the armor 800 along with sensors/actuators 50. As oneexample, FIG. 8B is a block diagram representation of an armor structurewith on-board data storage and off-board ASIC based structural healthmonitoring system. Here, the memory 202 is moved from within system 10to the armor 800 itself, affixed to the armor as a memory module 806. Insome embodiments, module 806 is preferably a solid state memory packageor chip that is placed in a protective housing. Embodiments can alsoinclude a chip package that is removable so that the memory can beupgraded or replaced, or its contents changed, relatively easily. In theembodiments of FIG. 8B, the memory module 806 remains electronicallyconnected to system 10, 300 as shown, so that processor 200 can stillretrieve or store information as necessary.

As another example, FIG. 9 is a block diagram representation of an armorstructure with ASIC module 900 located on-board the armor structure 800.Here, ASIC module 900 is coupled to the structure 800. Module 900 caninclude any one or more of ASICs 20 and 30, any other structuresutilized in their operation, and a protective housing. In particular, itmay be preferable to locate both ASICs 20, 30 on-board, as well as theirpower supplies 60, 306.

Here, the ASICs 20, 30 of module 900 communicate with a control station904 via a wireless transceiver 902. The control station 904 can be anydevice for directing any operations of the ASICs 20, 30 and/or receivingany resulting data. For example, the control station 904 can simply be adisplay, or it can be a portable computational device such as a handheldanalysis unit capable of directing the ASICs 20, 30 to initiate a scan(i.e., an interrogation) of the structure and displaying resulting datasuch as an indication of any damage the armor has sustained. In thismanner, the embodiment of FIG. 9 yields a compact, lightweight andportable system capable of determining the health of armor relativelyquickly, and in field conditions. It should also be noted that, whileFIG. 9 illustrates a wireless connection between module 900 and controlstation 904, embodiments of the invention can utilize any connectionbetween any components. For example, connections between any componentslocated on the structure and any other elements of monitoring systems10, 300 can be wired or wireless. Similarly, a wired or wirelessconnection can exist between the monitoring systems 10, 300 and anycontrol station 904 that may be present. Any ASICs or other structuresnot located on armor 800 can be positioned remotely, such as in controlstation 904.

As noted previously, the invention includes embodiments in which thesensors/actuators 50 are placed individually on structures such as armor800, and embodiments in which the sensors/actuators 50 are first placedon a flexible substrate, and the substrate is either affixed to orembedded within the structure. FIGS. 10 and 11 illustrate furtherdetails of this latter configuration. More specifically, sensors 50 areaffixed to flexible substrate 1000. Substrate 1000 also supports leads1002 that electrically connect/interconnect sensors/actuators 50 asdesired, and wires 1004 that connect sensors/actuators 50 to interface1006, to place sensors/actuators 50 in electrical communication with theremainder of systems 10, 300. The substrate 1000 can be shaped to fitthe structure as desired. Here, for example, the substrate 1000 isshaped to fit armor 800, so that it both fits within the spatialconfines of the armor 800 and generally conforms to its surface(s).

The substrate 1000 can be either affixed to an outer surface of armor800, or can be incorporated within. In particular, the substrate 1000can be embedded within modem multi-layer composite armor byincorporating it within layers during the armor's fabrication process.FIG. 10 illustrates examples of both configurations. In particular, theupper configuration of FIG. 10 shows an armor structure 800 made partlyof a composite laminate, ceramic plate, and ballistic nylon covering itsouter surface, followed by sensor/actuator layer 1000. Similarly, thelower configuration of FIG. 10 shows an armor structure 800 in which thesensor/actuator layer 1000 is sandwiched between the composite laminateand the ceramic plate, so that the sensor/actuator layer 1000 isembedded within layers of the armor structure 800 itself.

Embodiments of the invention having been described, one of ordinaryskill in the art will observe that the above-described components, aswell as their connections, attachments, and fabrication, can beimplemented in any manner. For example, the blocks of FIG. 2 can beimplemented as using known digital components and solid state devices,fabricated according to known methods. The electrical connectionsbetween sensors/actuators 50 and systems 10, 300 can be standard wires,electrical traces, or the like. Additionally, protective modulesemployed to protect components of the invention such as ASICs can be anyknown modules used to house and protect solid state electronics orassociated components. Also, components such as the above-describedMUXes can be any known multiplexing device or set of switches operableto direct signals to/from sensors/actuators 50, and separate MUX bankscan be implemented for actuators and sensors if desired. It is alsonoted that the solid-state components of embodiments of the inventioncan be packaged in any appropriate manner. For instance, ASICs 20 and 30can be implemented on the same silicon and packaged in a single chippackage, or can be implemented and packaged as separate chips. Indeed,the entire system (minus display) 10, 300 can be packaged as a singleintegrated chip, or any one or more components can be packagedseparately.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the invention.However, it will be apparent to one skilled in the art that the specificdetails are not required in order to practice the invention. Thus, theforegoing descriptions of specific embodiments of the present inventionare presented for purposes of illustration and description. They are notintended to be exhaustive or to limit the invention to the precise formsdisclosed. Many modifications and variations are possible in view of theabove teachings. For example, any one or more of the ASICs of theinvention, or their associated components such as power supplies,interfaces, transceivers or the like, can be located on-board oroff-board the structure they monitor. Additionally, thesensors/actuators 50 can be any sensors, any actuators, or anytransducers capable of acting as both sensor and actuator. Thesesensors/actuators can be located on a flexible substrate or individuallyplaced, and they (along with their substrate, if one is employed) can beaffixed to an outer surface of a structure or embedded within. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, to therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated.

1. A structural health monitoring system, comprising: a first integratedcircuit, comprising: a processing block receiving sensor signals fromsensors affixed to a structure, comparing the sensor signals to baselinesignals, generating results data from the comparing, and generatinginterrogation signals initiating transmission of interrogating signalsfor interrogating the structure; and a waveform generation blockreceiving the interrogation signals from the processing block andgenerating corresponding ones of the interrogating signals; a secondintegrated circuit, comprising: a signal conditioning block receivingthe sensor signals, conditioning the sensor signals, and transmittingthe conditioned sensor signals for receiving by the processing block ofthe first integrated circuit; and a multiplexer block routing theinterrogating signals to predetermined actuators affixed to thestructure.
 2. The structural health monitoring system of claim 1,wherein the sensors and the actuators are piezoelectric transducers. 3.The structural health monitoring system of claim 1, the processing blockfurther generating an actuator selection signal identifying thepredetermined actuators to the multiplexer block.
 4. The structuralhealth monitoring system of claim 1, the processing block furthergenerating a sensor selection signal identifying ones of the sensors tothe multiplexer block, the multiplexer block further routing the sensorsignals from the identified ones of the sensors to the first integratedcircuit.
 5. The structural health monitoring system of claim 1, whereinthe second integrated circuit further comprises a sensor signalamplifier block amplifying the sensor signals.
 6. The structural healthmonitoring system of claim 1, further comprising an interrogating signalamplifier block amplifying the interrogating signals.
 7. The structuralhealth monitoring system of claim 6, wherein the second integratedcircuit further comprises the interrogating signal amplifier block. 8.The structural health monitoring system of claim 1, wherein the firstintegrated circuit further comprises: an interface receiving theconditioned sensor signals, wherein the conditioned sensor signalsreceived at the interface are analog signals; and an analog to digital(A/D) conversion block in electrical communication with the interfaceand the processing block, the A/D conversion block converting theconditioned sensor signals from analog signals to digital signals andtransmitting the digital sensor signals to the processing block.
 9. Thestructural health monitoring system of claim 8: wherein theinterrogating signals generated by the waveform generation block aredigital signals; and wherein the first integrated circuit furthercomprises a digital to analog (D/A) conversion block receiving thedigital interrogating signals, converting the digital interrogatingsignals to analog interrogating signals, and transmitting the analoginterrogating signals to the multiplexer block of the second integratedcircuit.
 10. The structural health monitoring system of claim 1, whereinat least, one of the first integrated circuit and the second integratedcircuit is coupled to the structure.
 11. The structural healthmonitoring system of claim 10, wherein the structure is a ballisticprotective armor.
 12. The structural health monitoring system of claim1, wherein at least one of the first integrated circuit and the secondintegrated circuit is placed remote from the structure.
 13. Thestructural health monitoring system of claim 12, wherein the structureis a ballistic protective armor.